Re: Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.31-7
From: Ingo Molnar
Date: Wed Dec 01 2004 - 16:22:08 EST
* Mark_H_Johnson@xxxxxxxxxxxx <Mark_H_Johnson@xxxxxxxxxxxx> wrote:
> Unless I am mistaken, my "PK" config is the closest to 2.4 lowlat+preempt.
indeed, you are right.
> For the relevant differences in .config:
> PK RT
> CONFIG_PREEMPT_DESKTOP=y CONFIG_PREEMPT_DESKTOP is not set
> CONFIG_PREEMPT_RT is not set CONFIG_PREEMPT_RT=y
> CONFIG_PREEMPT=y CONFIG_PREEMPT=y
> CONFIG_PREEMPT_SOFTIRQS is not set CONFIG_PREEMPT_SOFTIRQS=y
> CONFIG_PREEMPT_HARDIRQS is not set CONFIG_PREEMPT_HARDIRQS=y
> (though the system still creates ksoftirqd/0 and /1 on both...)
> CONFIG_SPINLOCK_BKL is not set [not present]
> CONFIG_PREEMPT_BKL=y CONFIG_PREEMPT_BKL=y
> CONFIG_ASM_SEMAPHORES=y [not present]
> CONFIG_RWSEM_XCHGADD_ALGORITHM=y [not present]
> ...
> [not present] CONFIG_RT_DEADLOCK_DETECT=y
> ...
the only thing i'd suggest to change is to also generate an RT (and
perhaps PK) result with all debugging options disabled - i.e. both
RT_DEADLOCK_DETECT and all LATENCY_TRACING/timing related options
disabled.
but your tests did trigger asserts not so long ago so it might not be
wise to run without debugging. But it's definitely a thing to try in the
future.
> Unless you are saying that I should back off to one of the other
> preempt settings (to replicate the 2.4 config on 2.6).
no, i think the PK kernel is supposed to be quite close to what
2.4+lowlat offers.
Ingo
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